Do you guys have any tips for playing Janna?
Everything they said so far. Leveling up E first, and anticipating any incoming damage will help you and the adc stay up in lane longer.
Get a level in Q next. When youre using your cyclone, try to hit both their support and carry with it. An example would be if an enemy Leona jumps onto your adc. You will want to release the cyclone so that it will knock up both her and the adc to minimize incoming damage. If you can only hit one, make sure to hit the adc (that's basics, but still good to cover).
The fact that you can charge up your Q is great for a few reasons. You can hit distant enemies as they flee, since if it charges up all the way the distance it travels will be increased. Enemies are always changing positions. If you see them starting to make a move towards you, you can put down the cyclone and wait for them to get into a good position for you to knock them up.
I max W after E. It gives you movespeed and the single target slow is great. I generally won't even buy tier 1 boots until later on because of how fast Janna is with her W and passive. When running from enemies, especially just one, you need to decide if slowing them with W is better or if keeping your W up so you can run away faster is better. Generally I choose the latter, but it can be situational.
Your ult is great. The knockback + heal saves countless lives. Use it when the other team has a stronger engage than your own. I've had games that our team will be stronger offensively, so what you want to do in that situation is save your ult to peel and heal for your adc. If you're feeling frisky, a nice move you can pull off is to flash past the enemy team and use your ult to knock them into your team. Generally this is better in situations where you outnumber your enemies or are much stronger than them.
Janna is, if not the best, one of the best peelers in the game. I play her very defensively in teamfights and offensively in small skirmishes. Your movespeed along with Q and W are great for slowing down escaping enemies. Always have an eye on your adc in teamfights. Your Q + W + E + R + Exhaust should be more than enough peel to keep your team alive.
She's my most played champ in ranked, so if you have any other questions don't hesitate to ask. I'm sure there's some stuff that I forgot to touch on.